Variable-speed power-transmission mechanism



Patented Aug. 20, 1940 UNITI-:D STATES VARIABLE- SPEED ME PATENroFFmE POWER-TRANSMISSION V CHANISM H arold Sinclair, Remington, London, England l Application october 12, 193s, serial No.- 234,51'i

In Great Britain January 15, 1938 ,4 claims. (ci. u-isas) pling device in parallel. such as a mechanical clutch, or a hydraulic turbo-coupling of the variable-iilling type, whereby a direct drive can be established, that is to say a drive in which the torque-transmission ratio is 1 to 1.

Such turbo torque-converters commonly provide an output torque ranging from about 4.5 times the input torque when the output shaftis stalled, to la value equal to the input torque when the ratio of speeds of the driven and the driving,

shafts v nl attains a particular value such as depending on the design.

' Where it is desired to increase the lranges of torque and speed yielded by such a turbo converter, it is knownto couple to it in.series a mechanical change-speed gear, which `is capable of being changed while running, and which is arranged to be driven by the outputl shaft of the converter for the obvious reason that a converter requiredto absorb the normal power output of the driving engine when for example the output shaft is stalled must be run at only one input speed; or if the converter has a rising input speed characteristic with increase of secondary shaft speed, the driving engine must be capable of working over the corresponding range of power and speed if the full capacity of the engine and converter in combination is to be attained.

Since turbo torque-converters are relatively expensive to-put into production, it is convenient to adopt as few different standard designs as possible; and where such a converter is required to be used with a variety of standard types of driving engine with different normal rated powers and speeds, in most cases it' cannot be eniciently coupled directly to the engine, and a speed-increasing gearing of suitable constant ratio is usually employed to connect the engine to the converter sol a's to enable the size and weight of the converter to be reduced.

'I'he main object of this invention is to provide a power-transmission mechanism of the type set forth which yields ranges of torque and speed beyond those yielded by the turbo torque-converter alone, which is simpler than the known arrangements, and which is readily adaptable for has a value'of use with .engines of different rated powers and speeds. y

According to Vthis invention a power-transmission mechanism of the type set forth comprises aAmechanical change-speed gear which is capable of being changed while running and which isv arranged between the driving engine and the turbo torque-converter.-

adapted to yield a direct drive and aspeed-increasing drive, and the ratio of the speedsof its The mechanical change-speed gear may be a two-speed gear outputshaft, on the two din'erent drives respecv tively, .with a constant engine speed, may conveniently be approximately equal lto or somewhat narrower than the speed ratio of the turbo torque-converter when its torque ratio is 1 to 1. Where 1 the ratio of the speeds of the two-speed gear may usefully range between 1 to 1.2 `and 1.6.

'I'he mechanical change-speed gear may be a planetary gear having a friction clutch and a friction brake for engaging the respective speeds, such for example as a gear having electromagnetic clutch and brake devices of the Cotal type; or it may be of the synchro-self-shifting type with positive gear-selecting clutch and stop devices, asdescribed in my patent application Serial No. 169,973 filed October 20, 1937.

The torque-converter lMAY be `of the Voith type, as described in United States Patent No.

l 2,067,209, with reference to Fig. 6 thereof, having a turbo coupling in parallel and control means operable for maintaining at will only one or the other of the two turbo circuits filled Vat any one time; or it may be of the Lysholm-Smith or equivalent type,v as disclosed in United States Patent No. 1,900,119 having a two-way mechanical clutch for connecting the input shaft alternatively to the converter impeller and to the output shaft,-

the converter turbine being adapted to drive the output shaft through a disengag'eable clutch, for

example a free wheel; or the torque-converter may be of the synchro-self-shifting type hereinafter described.

In the accompanying drawings are shown diagrammatically a constructional example of the invention as applied to a locomotive driven by a Diesel engine, and .Y

Fig. 1 is a part-sectional plan of the powertransmission system,

Fig. 2 is a sectional elevation of a part thereof,l

taken on the line 2:2 in Fig. 1, and

' Fig. 3 is a graph showing the performancel of this system. y

The engine vI .in this example has anormal rating of 200 H. P. at 1400 R.. P. M. The torque'- converter which is generally denoted by 2, and

'which is shown as having a two-stage turbine but which may have anydesired number of stages, is designed to absorb 200 H. P. at 2000 R. P. M., and it yields a ratio of secondary torque M2 to primary torque MI equal-to i to when I'he engine is connected, if desired through a .shock-absorbing coupling such -as a hydraulic turbo coupling 3, to a planetary change-speed gear, which is generally denotedby 4` and which is capable of being changed while running. The driven shaft 5 of the turbo coupling 3 is xed to the planet-carrier 6 of the planetary train, while the annulus 1 is `fixed to the primary shaft 9 of vthe converter 2 and the sun wheel 8 is integral with a hub I0 to which is fixed an armature ring II engageable alternatively .with-an electromagnetic clutch element I2 xed on the annulus 1 to yield direct drive, and withan electromagnetic brake element I3 to yield a speed-increasing ratio of 1 to 1.43. the shaft 9, due to changing gear in the planetary gear, 'expressed as a ratio, is of the same order as the speed ratio of the torque-converter when its torque ratio is in the neighbourl'loodY of l to. 1.

The shaft 9 is directly connected to themir'ipeller I4 of the torque-converter and to its parallel alternative direct-drive coupling, which is gen-l The output shaft I6 oferally` denoted by I5. the torque-converter is connected to a driving axle I1 of the locomotive by the usual reversing .gearing I8 and reduction gearing I 9 of appropriate ratio. The reversing and reductionrgears are contained in a casing 26 which is journalled on .the axle vI1 and which is rigidly fixed to a bell housing 2I in turn fixed to a tubular housing 22 rigid with rthe engine I, the last -belng mounted on the locomotive frame by exible bearings (not shown) in known' manner.

The direct-drive coupling I5 of the converter 2,. which is a known synchro coupling as del scribed in Patent No. 1,862,188 of N. Legge, is arranged as follows. The primary shaft 9 is pro- Avided with left-hand helical splines 23 and with an axially splined collar 24. A nut 25 is engaged with the splines 23 `and is, provided with teeth 26 engageable with'teeth 21 on a drum 28 which is'fxed to thefshaft I6. One or more pawls 29 pivotally mounted onthe nut co-operate with the.

teeth 21 and are so positioned, relative to the teeth 26, as to cause the teeth26 and 21 to intermesh cleanly should the shaft 9 begin to lag behind the shaft I6, when they are rotating in the' forward direction, as shown by the arrow A. A

locking sleeve 30 provided with internal axial housing. i

The turbine 36 of" the converter 2 is fixed to the drum 28` on the output shaft I6, and the :reaction blading 31 of the converter is xed in 'I'hus the change of `speed of a casing 38 free to rotate in the forward direcltion, but prevented from rotating-backwards by a Legge synchro-coupling comprising left-handed helical splines 39 on the casing boss and a'nut 40 having teeth 4I engageable, under the control of pawls 43, with a toothedannulus 42 ilxed` to the bell housing 2l. v

, The change-speed gear4 and the direct-drive coupling I5 are preferably provided with interlocked control mechanism.v A control handle has the form of a switch blade d5 electrically connected` through a battery` 46 to earth. The blade 45 co-operates with contacts 41, 48, 46 and 50. 'Ihe contacts 41 and 48 are connected by a conductor 5I to one terminal of the winding of I the brake element I3, the other terminal of which is earthed. 'Ihe contact 49 is connected by a conductor 52 to a brush 53 co-operating with an electrically insulated. slip ring 54 which forms one terminal of the Winding of the clutch element I2, theother terminal of which is earthed.

"I'he contact 50 is connected -by a conductor 55 to one terminal of the winding of a solenoid 56 arranged, when energized, to rock the yoke 3l so as to urgel the striking ring 32 to the'lei't. A spring 51 biases the yoke in the opposite dlrecetion. The other terminal of the solenoid lwinding is earthed. Four positions of the control member 45 are denoted by N (neutral) and GI, G2 and G3 (low, middle and high speeds).

In starting from rest the control member 45 is moved from position N to position GI, so that the brake element is energized and the planetary unit Ms accordingly put in high gear. The converter is operative since the direct-drive coupling l5 is disengaged. If the converter has a constant input speed characteristic, the converter input shaftaccordingly runs at a speed of 2000 R. P. M. absorbing the full power of the engine at its normal speed of 1400 R. P. M. and the locomotive accelerates under a torque in the output shaft I6 of the converter equal to 14 M2 20M"M1 where Mm is the engine torque.

In Fig. 3 (where the engine torque is taken as constant), th'e horizontal scale denotes speed of the converter output shaft 'I6 in R'. P. M.; the ordinate scale M2 denotes the torque in the shaft I6 in terms of the engine torque as unity; the ordinate scale um is the engine speed; and n is the efficiency of transmission from the engine to the shaft I6. Ihe parts of the nm curve marked (a.) and (b) refer to converterswith a constant, anid a rising, input speed characteristic respectively.

When the speed of the converter output shaft I6 reaches about 1100 R. P. M.

M1 will be about 1.5 to 1, so that further acceleration on the converter drive, becomes less eiiicient than by changing to direct drive throughout. The system is accordingly changed to its condition for normal running'by moving the control member 45 to position G2 and momentarily retarding the engine. The brake element I3 vis deenergized andthe clutch element I2 is energized, so that the planetary gear 4 changes down to direct drive. The solenoid 56 is also energized, so that the striking ring 32 and the locking sleeve s3l) are urged to the left. Since at first the splines inthe locking sleeve are out of register with the splines on the collar 24, the locking sleeve is unable to engage this collar. However, as soon as the speed of the shaft 9 begins to drop below that of the shaft IB, the nut 25 is moved to the left, bringing these splines in register so lthat the locking sleeve 30 engages the collar 24. The engine is now caused to generate power,4 and, as the nut 25 is prevented by the sleeve 30 from rotating Arelatively to the shaft 9, the directdrive coupling remains engaged. The engine speed and the speed of the shaft I5 'will be about 1100 R. P. M. and the torque in this shaft will be equal to the engine torque Mm, since the drive is direct throughout.

The simultaneous changing of the mechanical gear to the lower-speed ratio and of the converter to direct drive,*which effects the change from low or starting speed to themiddle or normal speed in the system as a whole, is an important feature of this invention, since it enables the. converter tobe cut out of action, without any abrupt drop in the output torque M2 in consequence ofthe change, before the converter eiciency has dropped substantially below its maximum value. It will be apparent from Fig. 3 that, if the converter were merely changed to direct drive, without any complementarychange of gear in the mechanical gearing, there would be either an abrupt drop in output torque M2, if the change were made near the point of maximum converter emciency, or the converter would operate on an ineilicient part of its characteristie curve if the change were delayed until an abrupt drop in the output torque curve was avoided.

By moving the control member 45 to position G3 the mechanical gear I is changed to the high ratio and the converter 2 is left in direct drive, so that an over-drive speed-is obtained, in which, when the engine speed is 1400 R. P. M., the speed of the converter output shaft is 2000 R. P. M., as suited forl a high cruising speed of the vehicle under easy running conditions.

An alternative change pOint between nrst and second speeds, at a value of m of about 950 R. P. M. is indicated in Fig. 3 by faint dotted lines.

'I'he improved transmission mechanism may be advantageously employed on vehicles driven by internal-combustion engines on tropical mountainous routes, in order to compensate for the variation in maximum power output of the engine with changed altitude and temperature when a variable supercharger is not employed. 'Ihe power output of the engine may fall by say 30 per cent. under conditions .of high altitude accompanied byhigh temperature in the courseof a journey, and as the power absorbed by the torqueconverter varies as the cube of the speed lof its input shaft, the change-speed gear between the engine and the converter may provide alternative ratios which will enable the converter to utilize nearly the full power available when climbing at 'various altitudes, in addition to providing an intermediate direct drive gear of high eiliciency.

Referring to Fig. 1, when the control member l5 is moved to the emergency position GE, it energises a contact which is connected to the conductor 52, with the result that the planetary l gear it put into direct drive while the converter remains operative. Thus, although the.engine,-

owing to the atmospheric conditions. is able to f generate onlyla part of the normal maximum converter through the direct drive, instead of the overdrive ratio, in the planetary gear.

I claim:

l. A power transmission system comprising an engine, a turbo torque-converter, an auxiliary coupling device in` parallel with said torque-converter whereby a direct drive can be established, control means for said auxiliary coupling device, and a mechanical change-speed gear which is capable of being changed while running' and which connects said engine to said torqueconverter, the characteristic of said torque converter and the ratio of a higher-speed gear in said mechanical gear being such that, when said torque-converter isoperative and said higherspeed gear is engaged, said engine can attain substantially its normal continuous-rating torque and speed.

2. A power transmission system comprising an input shaft, a turbo torque-converter, an auxiliary coupling device in parallel with said torqueconverter whereby a direct" drive can be established, a mechanical change-speed gear which is capable lof being changed while running and which connects said input shaft to said torqueconverter, and a common control member operatively 'connected with means for engaging said auxiliary coupling device and with means for changing gear ratio in said mechanical gear, said control member being operable to cause `a highspeed ratio to be established in said mechanical gear when said auxiliary coupling device isdisengaged, and to cause alternative speed ratios to be established in' said mechanical gear when said auxiliary coupling device is engaged.

3. A power transmission system comprising an engine, a turbo torque-converter, an auxiliary coupling device in parallel with said torque-converter whereby a direct drive can be established, control means for said auxiliary coupling device, and a mechanical change-speed gear which is capable of'being changed while running and of yielding a low-speed ratio drive and a high-speed ratio drive and which connects said engine to said torque converter, the ratio of the speeds of the output shaft of said gear, on said two drives respectively, with a constant speed of said engine, being not substantially wider than the ratio of the output speed to the input speed of said torque converter that exists when its torque ratio is 1 to 1, and the ratio of said high-speed ,ratio drive being so selected in relation to the drive having a speed ratio between 1 to 1.2 and1 1 to 1.6, and which connects said input shaft to said torque converter, and control means for said auxiliary coupling device and said mechanical gear, said control means being operable to maintain said auxiliary coupling device disengaged while said speed-increasing drive is engaged.

HAROLD SINCLAIR. 

